The present invention relates to a chain conveyor.
Such chain conveyors are used in particular to convey bulk materials. In years past such chain conveyors have been used increasingly in basis materials industries (e.g. in coal mining or cement manufacture) to meter or determine the feed rate of bulk materials, since they facilitate a construction which resists wear with high throughput on account of their large abstraction power. In addition a chain conveyor is relatively inexpensive to make and service and can be set up without problem, so thatxe2x80x94because of its robust constructionxe2x80x94it is suitable as a hopper abstraction unit even for abrasive, coarse grained or sticky bulk materials, as is described in ZKG (Zement-Kalk-Gips [=Cement-Chalk-Gypsum]) No. 7/1993, p. 380.
A disadvantage with the usual structure of a chain conveyor is however that the metering accuracy is relatively poor, since the volumetric filling can be very non-uniform on account of differing densities and also conveyed material can adhere to the conveyor chain connecting the entraining bars during the emptying. Appreciable deviations in respect to the metering accuracy can result from this, which is particularly serious for aggregate mixtures.
Scales combined with belt conveyors or plate conveyors are already known, e.g. according to DE 19 536 871 or DE 4 230 368, wherein the conveyor belt or the plate belt runs over a positionally fixed weighbridge. However, these conveyors have disadvantages in relation to their wear characteristics or the required energy demand, since on the one hand conveyor belts of rubber materials suffer from a lot of wear, even when reinforced, and on the other hand plate belts have a lot of friction, on account of the relative movement between the individual articulated members, especially when heavily loaded.
The invention is accordingly based on the object of improving the metering accuracy of chain conveyors, with a simple construction.
The support of at least a partial region of a measuring segment, especially of a measuring bridge, on at least one force measuring device, results in precise gravimetric control over the amount of material transported by the chain conveyor. In this way, irregularities such as are unavoidable from differing filling levels in volumetric metering, are reliably avoided and material adhering to conveyor chains and the like can be detected, while the set-point metering amount can accordingly be maintained precisely in the manner of a metering scale with regulated drive. Because of the definite guiding of the conveyor chain in the region of the measuring segment, disrupting forces, e.g. from jamming of granular material between the entraining members and the measuring bridge, can largely be eliminated, so that the measuring segment itself is largely free from external forces, in the manner known from technical mechanics as xe2x80x9cisolatedxe2x80x9d, even in the case of very high chain tractive forces. A closed system unit results from guiding the conveyor chain in the region of the measuring segment, where the conveyor chain is securely held down. This can be assisted in a simple way by a slightly peaked form of the measuring bridge, so that a predetermined pre-load on the measuring segment arranged in the tight run results, which reliably avoids lifting of the conveyor chain even with slackening or varying chain tension. Thus problems with unequal feed, such as can occur in the arrangement in the slack run free from tractive force, are likewise reliably avoided.
A particularly simple design of the proposed chain conveyor results in that the measuring bridge of the chain conveyor is pivotally arranged at a defined axis arranged preferably centrally in the plane of circulation of the chain and the weight or force measuring device is spaced from this axis. This arrangement is particularly suitable for retro-fitting of existing chain conveyors in the tight run with guiding of the conveyor chain on the measuring segment, since retro-fitting of the chain conveyor with the gravimetric force measuring device is possible by simple fixing of bolts or other bearings forming the axis, e.g. also of drag-link conveyor apparatuses.
The same applies to movable mounting of only a part of the measuring bridge, which is decoupled by flexible intermediate elements. By interposing flexible intermediate elements, especially composite rubber-and-steel bars or weakening of the material in the manner of a film hinge and support on the measuring device, a simple retro-fitting of existing chain conveyors can be achieved.
A particularly advantageous design has two measuring bridges, where a second tare measuring bridge is arranged before the inlet or hopper feed opening and after the outlet opening, so that the actual discharge amount at the outlet opening can be determined and a tare measurement can thus be effected. The arrangement of two bridge parts, which are connected to one another by a link and act on only a single force measuring device in the manner of a weigh beam, is possible for detecting the chain and entraining member weight in a simple way.